It has been known since the middle of the nineteenth century that geomagnetic storms can affect the operation of systems that comprise long electrical conductors. A written report of the adverse effects of one such storm on electrical power systems was published in 1940. Among the noted effects were tripped transformer banks, blown transformer fuses, reactive power surges, and significant currents on neutral lines.
More recently, on Mar. 13, 1989 the Hydro-Quebec power system collapsed, with significant damage to equipment. It took more than 9 hours to restore 83% of full power. Among the damaged equipment were generating station step-up transformers, shunt reactors, thyristors and capacitor banks. It is now considered a certainty that this black-out was caused by a magnetic storm.
Geomagnetic storms, also referred to as solar-magnetic disturbances (SMDs), can cause the flow of large currents in appropriately located and oriented conductors on Earth's surface. These "geomagnetically-induced currents" (GICs) can cause, inter alia, severe offset saturation of power system transformers, which in turn can result in overheating. Furthermore, the saturation results in the introduction of harmonic currents into the system. These harmonics can overload capacitor banks and cause misoperation of static power devices. Relay and protection systems are also affected by the harmonic currents. These and other effects of SMDs can result in severe system disruptions, exemplified by the above referred to black-out of Mar. 13, 1989.
Electrical power installations are not the only installations that have in the past been affected by SMDs. For instance, an outage of a link of the L4 continental coaxial telephone cable occurred on Aug. 4, 1972 during a large geomagnetic storm, and is believed to have been caused by the storm (C. W. Anderson III et al., The Bell System Technical Journal, Vol. 53(9), pages 1817-1837). Disruptions due to SMDs have also occurred on oceanic telecommunications cables.
A considerable amount of research has been conducted on SMDs, on their effect on electrical power and telephone systems, and on ways to mitigate the effect of GICs on such systems. See, for instance, V. D. Albertson and J. G. Kappenman et al, both in Conference on Geomagnetically Induced Currents, Nov. 8-10, 1989, Burlingame, Calif. (both incorporated herein by reference). See also the article by J. G. Kappenman et al. in IEEE Spectrum, pp. 27-33, March 1990, also incorporated by reference.
J. A. Joselyn et al. (also incorporated herein by reference), at the same conference (which was sponsored by EPRI, the Electric Power Research Institute), reviewed SMD-related services provided by SESC, the Space Environment Services Center, a joint operation of the U.S. Department of Commence and the U.S. Air Force. The SESC collects data on natural variations in Earth's magnetic field (B) and converts these data to the so-called "K index", a number from 0 to 9. K index values are determined at 3-hour intervals, and neither contain any information on the time rate of change of B nor do they contain information on the spatial scale of a disturbance, except possibly on a very large (more than 1000 km) scale. If the observed K index for Boulder, Colo. (SESC is located in Boulder) exceeds 4, 5 or 6, SESC issues "alerts" to selected institutions that include some electric utilities. Such an alert informs the recipient that a disturbance has occurred, and that additional K's or 4 are expected for the next 12 hours. SESC also issues alerts (based on a running index based on the eight most recent K index values) that inform recipients that the disturbance has lengthened into a storm.
Those skilled in the art will know that SESC's alerts are based on past events and do not provide a basis for reliably anticipating severe future SMDs that could affect the operation of power grids and other systems comprising long electrical conductors. Indeed, operators of such systems currently generally are not aware of the occurrence of SMDs. G. A. Cucchi of the PJM Interconnection Office, in a paper (also incorporated herein by reference) at the above referred-to EPRI Conference, stated the following: "On Mar. 13, 1989 at 0245 EST the Hydro Quebec System went black. It was not until 0400 EST that operators realized that a Solar Magnetic Disturbance (SMD) of K9 intensity had occurred and was probably the cause of thousands of customers in Quebec Province being without electricity for up to nine hours." The author went on to relate that the SMD resulted in a loss of nearly 1,000 MVARs, (megavoltampere reactive) and that " . . . plant personnel throughout North America described transformers sounding like jet aircraft".
But even if operators were aware of recent significant SMDs, this typically would not permit the timely taking of preventive action. G. A. Cucchi (op. cit.) has stated as follows:
"Operating procedures fall generally into two categories, namely, preventive action and corrective action. The key to preventive action is the ability to forecast the event with sufficient accuracy and lead time. The "K" and "A" alerts and warnings which have been issued by the NOAA's Space Environment Services Center (SESC) in Boulder, Colo. and by the Geophysics Division, Geological Survey of Canada, Energy, Mines and Resources (EMR) in Ottawa, Ontario are simply not adequate for the power system problem. Both scales, for example, represent average conditions over three and 24 hours, respectively. The three-hour or K scale is used most often, particularly to report past conditions. The open-ended, logarithmic K scale covers a wide range of activity at the highest or K9 level. On the power system, I have seen K9 events go unnoticed where, most recently, on Sep. 19, 1989, a K7 storm has caused damage to transformers and system components."
Cucchi further states that the presently available alerts are not very useful, and goes on to say:
"For SMD protection, the likely operating procedures would involve protecting the voltage profile of the system and protecting against transformer damage. Normally, system operation protects against the most severe single contingency. To protect against multiple capacitor trippings and the resultant VAR loss, operators would unload transmission by reducing economic transfers to maintain an abnormally safe voltage profile. To protect against transformer damage, operators would dispatch selected generators to minimum loading levels or, in the extreme, remove the generator from the network. We estimate in PJM, for example, that since Mar. 13, 1989 if we responded to every K alert of level 5 or greater, PJM would have spent over $100 million in excess incremental operating costs." After expressing the desire for accurate forecast data designed specifically for the needs of the electric power system, Cucchi states as follows:
"If forecasting accuracy cannot be improved, operating procedures must lean toward corrective action. For example, if SMD had a unique signature that would respond to pattern recognition, a human or a computer could respond to the beginnings of an event. Five to ten minutes notice would be sufficient to reconfigure the system dispatch to a more secure state . . . . "
In view of the immense economic significance of avoidance or mitigation of the effects of SMDs on the electric power grid and other installations that comprise long electric conductors, a method of operation of such an installation that comprises obtaining data that permits taking installation-protective action would be of great importance. This application discloses such a method.